This invention relates to a water purifying system through denitrifying reduction with facultative anaerobes, which is used in an appreciation preserve for breeding aquatic creatures mainly consisting of ornamental fishes such as tropical fishes, freshwater fishes and saltwater fishes, or invertebrata, turtle and the like, or a preserve for breeding edible fishes and shellfishes.
As this type of the anaerobic water purifying system, there has hitherto been proposed a technique wherein a thick partition including a main reaction space composed of a porous or fibrous substance is formed inside a reaction apparatus between a volume of water to be treated and a volume of water enclosed in a single and means for maintaining concentration gradients of various dissolved substances is arranged in this space to diffuse various microorganisms for purification as is disclosed, for example, in Japanese Patent No. 2665789. And also, there was hitherto been proposed a technique wherein a partition plate provided with many water-passing holes is arranged inside a closed case not permeating a light and food balls as a spherical filtering material including a component growing anaerobic bacteria are filled in one chamber partitioned by the partition plate and a pipe passing water through the chambers formed by the partition plate is attached to control the increase of nitrate included in water in the water tank and decrease the number of water changes.
For example, in the system disclosed in the above Japanese Patent No. 2665789, however, it is inconvenient to take a fairly long times for stabilizing the anaerobic bacteria. Also, a large amount of sand is placed in the water tank, which is appreciatorily indecent, but it is possible to breed corals, few fishes or the like not requiring much food. However, this system do not follow to the decomposition treatment of the nitrate stored day by day, so that it is difficult to breed fishes and corals requiring a greater amount of the food. As a result, the change of water is forcedly conducted, and it is difficult to stabilize water quality and breed a greater number of fishes and the like. Furthermore, there is a circulation type box-like apparatus containing food balls for anaerobes as a conventional technique. However, such a circulation type has problems that the circulating rate approximately equal to dropping does not follow to the decomposition of the nitrate stored day by day in the water tank, and it is difficult to hold a non-oxygen water region as the circulating quantity becomes faster, and the like. Also, it has been confirmed that water filtered through anaerobic circulating water path is returned to aerobic circulating water path to return nitrogen denitrified in the anaerobic circulating water path to water breeding aquatic creatures and this nitrogen component obstructs the growth of invertebrata such as corals, shellfishes and the like. Further, the food balls to be supplied to the anaerobes (organic substance consisting of methanol, methyl alcohol or the like as a main component) melt into the breeding water to whiten the breeding water, which gives a bad influence to the breeding creatures and aerobic filtering bacteria. Moreover, concentrations of ammonia and nitrate are raised to bring about the death of the breeding creatures.
The invention is discovered based on the conventionally existing circumstances as mentioned above and is to provide a water purifying system through denitrifying reduction with facultative anaerobes in which a nitrate harmful in the breeding of creatures such as fish, coral and the like is efficiently decomposed in a short time so as to conduct the denitrifying reduction as compared with the conventional water purifying system with anaerobes and a nitrogen component is separated and removed from water for breeding and the number of water exchange is decreased as far as possible to reduce a purification cost and labor for water exchange.
According to the invention, an aerobic circulating pathway of water reduced through a filter using aerobes and an anaerobic circulating pathway of water reduced through a filter using anaerobes are separately arranged, and a nitrate produced in the aerobic circulating pathway is exuded into the anaerobic circulating pathway through sand or a water-permeable and oxygen-impermeable screen member separating the aerobic circulating pathway and the anaerobic circulating pathway, and the nitrate is decomposed in the anaerobic circulating pathway arranged independently from the aerobic circulating pathway.
Furthermore, a nitrogen gas produced when the nitrate is decomposed in the anaerobic circulating pathway is discharged at a state of isolating so as not to contact with water in the aerobic circulating pathway. And also, the anaerobic circulating pathway is disposed on a bottom or a side face part of a water tank for breeding of aquatic creatures, or on a bottom of a water chamber adjacent to an exterior aerobic filter tank connected to the water tank for breeding the aquatic creatures, or a bottom side of the aerobic filtering tank.
Further, a box type anaerobic bottom filter body constructed by perforating plural holes in an upper plate part so as to render into a draining board, and arranging a pair of shower pipes for drainage and discharge each connected at its opening end side to a closed type anaerobic filter device and provided with plural jetting holes in its longitudinal direction so as to locate in an inside of the filter body at both opposed ends thereof is arranged on a bottom part of the water tank for breeding the aquatic creatures, and powdery sand or the water-permeable and oxygen-impermeable screen member is placed on an upper face of the draining upper plate part of the anaerobic bottom filter body, and water existing inside the anaerobic bottom filter body is circulated through the closed type anaerobic filter device to conduct reducing treatment and contacted with the powdery sand or the screen member located on the upper face of the draining upper plate part through the holes.
In addition, a box type anaerobic bottom filter body constructed by perforating plural holes in an upper plate part so as to render into a draining board, and arranging a pair of shower pipes for drainage and discharge each connected at its opening end side to a closed type anaerobic filter device and provided with plural jetting holes in its longitudinal direction so as to locate in an inside of the filter body at both opposed ends thereof is arranged on an inner bottom part of a water chamber adjacent to the aerobic filtering tank arranged outside the water tank for breeding the aquatic creatures or at a bottom side of the aerobic filtering tank, and powdery sand or the water-permeable and oxygen-impermeable screen member is placed on an upper face of the draining upper plate part of the anaerobic bottom filter body, and water existing inside the anaerobic bottom filter body is circulated through the closed type anaerobic filter device to conduct reducing treatment and contacted with the powdery sand or the screen member located on the upper face of the draining upper plate part through the holes.
Moreover, a pair of shower pipes for drainage and discharge each provided with plural jetting holes in its longitudinal direction so as to locate in an inside of the filter body at both opposed ends thereof is arranged in an inside of a lower-stage chamber formed on an upper face side with punch board at both ends thereof, and powdery sand or a water-permeable and oxygen-impermeable screen member is filled in a middle-stage chamber located between the punch board of the upper face side of the lower-stage chamber and a permeable screen arranged above the punch board, and a unit type reducing filter box of a filtering tank throwing system filled with a rough sponge pad or gravel is arranged inside an upper-stage chamber between the permeable screen and a punch board arranged above the permeable screen.
In the anaerobic circulating pathway is arranged a cylinder type exuding hollow body constructed by covering a pipe provided on its side face with holes with a net-like covering member, and the cylinder type exuding hollow body is disposed in the bottom of the water tank as an anaerobic bottom filter body.
Further, a cylinder type exuding hollow body is formed by covering a pipe provided on its side face with holes with a net-like covering member, and a pair of such cylinder type exuding hollow bodies are arranged on upper and lower sides of a closed box, and powdery sand is filled in the inside of the box to serve the upper cylinder type exuding hollow body as an aerobic circulating pathway and the lower cylinder type exuding hollow body as an anaerobic circulating pathway.
In the anaerobic water purifying system for breeding aquatic creatures having the above construction according to the invention, the nitrate produced in the aerobic filtering tank is decomposed in the anaerobic circulating pathway separated independently from the aerobic circulating pathway of water. By exuding the nitrate from the aerobic circulating pathway to the anaerobic circulating pathway to decompose in the anaerobic circulating pathway separate independently from the aerobic circulating pathway is efficiently denitrified and reduced the nitrate in the water tank in a short time.